The present invention relates to an NC (numerically controlled) machining system in which a machining head is controlled by NC control device to machine a workpiece to a desired configuration. More particularly, the invention relates to an NC machining system in which a plurality of turrets are simultaneously controlled.
In a conventional NC machining system, the position of a tool relative to a workpiece is controlled by numerical information specifying the position of the tool. This numerical data is provided by an NC control system. With such a system, a workpiece can be machined to a complex shape with high accuracy and at a high rate, thereby yielding high productivity.
Generally, an NC machining system is constituted, as shown in FIG. 1, by an NC control device 20 which operates upon numerical information inputted by a terminal 10, and an NC machining device 30 which is controlled by the numerical values provided by the NC control device 20. The NC control device 20 includes an input section 21 through which externally supplied instructions are inputted, a computing section 22 for operating upon the instructions received via the input section 21, a memory section for storing results of operations performed by the computing section 22, a control section 24 for controlling the operation of the computing section 22, an output section 25 for sending computed values produced by the computing section 22 to the NC machining device 30, and the display section 26, which includes the keyboard, for inputting and displaying the data, including the data received via the input section 21, the outputs produced by the output section 22, and the contents of the memory section 23.
The machining device 30 includes a tool 31 attached to a tool holder 32, which is in turn attached to a chuck of a spindle 33. The splindle 33 is rotated by a spindle motor drive 34, which is in turn driven by a signal provided by the output section 22 of the NC control device 20. A workpiece 40 is fixed to a table 35 of the machining device 30 by a jig or the like. As indicated in FIG. 1, a screw 36 is provided for moving the table 35 in the direction of the X axis. The screw 36 is driven along the X axis by a motor 38 through a gear box 37. The motor 38 is controlled by a signal produced from the output section 25 of the NC control device 20. Similarly, screws, motors and gear boxes are provided for moving the table 35 in the Y and Z directions in response to signals produced by the output section 25 of the NC control device 20.
It as previously been proposed to provide a lathe with a plurality of rotating tools. An example of such a lathe is shown in outline form in FIG. 2. As shown in FIG. 2, a cylindrical workpiece 110 is held at one end by a chuck 101, the latter being rotated around the Z axis. The other end of the workpiece 110 is supported by the tip 102a of a tail stock 102. Cutting tools 105 and 106 are provided for cutting the workpiece 110. The tools 105 and 106 are fixed to first and second turrets 103 and 104, respectively. To cut the workpiece 110, the first and second turrets 103 and 104 are moved in the direction of the Z axis.
Conventionally, the instructions for moving each turret are supplied to the NC control device 20 externally. This is done utilizing a so-called G code, which is a language peculiar to the field of numerical control. Accordingly, an NC machining system of this type cannot easily achieve fully automatic programming in which various data, such as data indicating the type of the cutting tool, cutting conditions, and the like, are supplied by a keyboard associated with the display section 26. Further, the conventional system suffers from a drawback in that it is very difficult to instruct and control the operation of two cutting tools simultaneously.